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Wrapping core components for kotlin code generation with kotlin-poet.

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package io.toolisticon.kotlin.generation.spi

import com.squareup.kotlinpoet.ExperimentalKotlinPoetApi
import java.util.function.BiPredicate
import kotlin.reflect.KClass
import kotlin.reflect.full.isSubclassOf

/**
 * Root interface for code generation spi.
 *
 * This is a sealed interface, the only allowed subtypes are:
 *
 * * [KotlinCodeGenerationStrategy] - the build plan of a spec using input and context
 * * [KotlinCodeGenerationProcessor] - visitor pattern to modify spec builders before the spec is build.
 */
@ExperimentalKotlinPoetApi
sealed interface KotlinCodeGenerationSpi, INPUT : Any> : Comparable>, BiPredicate {
  companion object {
    val metaInfServices = "META-INF/services/${KotlinCodeGenerationSpi::class.qualifiedName}"
    const val DEFAULT_ORDER = 0
  }

  /**
   * The name that is used when the implementing class is listed in a `META-INF/services/` file.
   * Attention: SPI uses java naming, so inner classes have to be separated by `$`.
   */
  val name: String

  /**
   * The type of the generic INPUT, used to filter relevant instances.
   */
  val inputType: KClass

  /**
   * The type of the generic CONTEXT, used to filter relevant instances.
   */
  val contextType: KClass

  /**
   * Order is used to sort spi instances.
   */
  val order: Int

  /**
   * Compare by order to sort list of SPI instances.
   *
   * @param other the other spi instance
   * @return -1,0,1 as specified by [Comparable]
   */
  override fun compareTo(other: KotlinCodeGenerationSpi<*, *>): Int = order.compareTo(other.order)

  /**
   * If `true`, the spi instance is executed, else ignored.
   *
   * @param context the context we are operating in
   * @param input the concrete work item, for the check this is unbound and nullable, so we can check against calling with unsupported types.
   * @return `true` when the spi shoud be applied.
   */
  override fun test(context: CONTEXT, input: Any): Boolean = context::class.isSubclassOf(contextType) && input::class.isSubclassOf(inputType)
}